1. Field of the Invention
This invention relates to a key telephone system. More particularly this invention relates to a key telephone system so configured that every key telephone set in the key telephone system will be enabled to utilize, on the basis of common use, the same abbreviated dialing, automatic dialing, service class, and user data such as extension numbers.
2. Description of the Prior Art
The conventional key telephone system, as widely known, comprises a key service unit and a plurality of key telephone sets connected to the key service unit through connecting cables. In recent years, adoption of electronic devices in the key telephone systems of this class has advanced to a point where their key service units incorporate therein, as a control circuit, a microcomputer (CPU) adapted to effect various controls.
This electronic control circuit is composed of a control circuit (CPU), a read-only memory (ROM) serving to provide the control circuit (CPU) with a program, a random access memory (RAM) functioning to store necessary data and specifying work areas, and various buses such as data bus, address bus, and control lines.
In the key telephone system of the kind incorporating electronic devices as described above, various data are transmitted and received during the transfer of information between the key service unit and the individual key telephone sets. Broadly, these data are classified as being one of the following three kinds.
(1) Control data (control program data) based on the programs forming the foundation of a given system which are of a permanent nature.
(2) General system data established for a given system based on such system functions as setting telephone sets so as to be capable of issuing a sound on reception of a call, setting the dial pattern (DP/MF) of an office line introduced to the key service unit, and setting calendar and clock (hereinafter referred to as "system data").
(3) Individual system data established by, and subject to change by, an individual user in conformity with conditions of use, places of installation, and methods of use on the part of the user, as in assigning numbers (such as *01) for abbreviated dialing, setting dial data corresponding to the assigned numbers, and setting the day-night switch of service class, for example (hereinafter referred to as "user data").
The control data are characteristic of a given system and absolutely invariable. They are fixed in form at the time that the system is shipped as a product from the factory. The system data are such that when a user places an order for a key telephone system including a specification, for example, such that all the key telephone sets are to be adapted to issue a sound on reception of a call, the data are established to conform with the user's order at the time that the system is shipped as a product or at the time that the system is installed in the user's office. The user data are such that, after the system has been installed at a user's office, the data can be freely altered to suit the user's own convenience at any time he pleases.
In the conventional key telephone systems of the kind incorporating electronic devices, more often than not user data corresponding to abbreviated dial function of the aforementioned RAM, automatic dial transmission function, and service class function are established for the individual key telephone sets. In a company, for example, the key telephone system may be configured so that the key telephone set installed in the secretarial section will be put in at a terminal keeping in registers the whole user data and provided with all the possible telephone functions, while in the key telephone sets for all the company employees, Mr. A's telephone set will be so set as to control making of toll transmissions, Mr. B's will be so set as to control the making of automatic dial transmissions and the making toll transmissions, and others will be so set as to control performing functions that are different one from another. The key telephone system may otherwise be configured so that different sets of user data will be provided in separate registers for individual key telephone sets grouped by the unit of department and the unit of section, for example. In the case mentioned above, therefore, Mr. A and Mr. B are compelled to go to the secretarial section and borrow the telephone set installed therein for the purpose of making a toll call and, in the meantime, any of the employees at the secretarial section who has left his own seat is not enabled to make a toll call at Mr. A's or Mr. B's seat.
In the conventional key telephone system, the user data registered in the RAM of the key service unit correspond fixedly to the individual key telephone sets as described above. This fact entails the disadvantage that when a person happens to leave his seat, move to some other person's desk, and borrow the key telephone set there, therefore, he will have restrictions in various functions of the borrowed key telephone set, such as the procedure of transmission, because this key telephone set may possibly be set so as to permit functions different from those of the key telephone set to which he is accustomed at his own seat.